1. Field of the Invention
The present invention relates to a cleaning apparatus using a blade for removing toner remaining on the surface of a toner image retaining member.
2. Description of the Prior Art
When an electrostatic recording apparatus in which a flat and smoothly surfaced photosensitive substance such as selenium, organic photoconductor or cadmium sulfide, or dielectric such as polycarbonate, is used, it is necessary to clean up toner remaining on the surface of the toner image retaining member such as photosensitive substance or dielectric.
For an effective cleaning method, there is known a method for the purpose by making use of an elastic blade. So far, for a blade cleaning means, there are known two types as shown in FIG. 1 and FIG. 2. In the known devices, an elastic blade 2 supported by a holding means 3 is brought into contact with a drum-shaped and clockwise rotating toner image retaining member 1 at a point of contact A. Let .phi. be the angle between the tangent X--X of the drum which touches the circle at point A and an axial line Y--Y of holding means 3 at the pre-cleaning side 1a on the surface of said drum. The known devices can be considered as there are two types, where .phi.&gt;.pi./2 and .phi.&lt;.pi./2.
(1) In the type where .phi.&gt;.pi./2 (Refer to FIG. 1)
In this type, as the toner image retaining member moves, the blade is bent to the cleaning side and is squeezingly deformed by a friction force between the toner image retaining member and the blade, and by the reaction force thereof the edge of the blade comes into heavy pressure contact with the toner image retaining member. Accordingly, the performance for cleaning remaining toner is great. However, as a defect thereof, there is the possibility of damaging the surface of the toner image retaining member by applying an excessive force. The afore-mentioned friction force actuates the blade to be squeezed longitudinally and a little change where the friction force makes the blade flutter.
(2) In the type of .phi.&lt;.pi./2 (Refer to FIG. 2)
There is no actuation of a strong reaction force from the blade caused by the friction force between the blade and the toner image retaining member, Accordingly the inconvenience caused in the type (1) does not occur in this type. On the other hand in this type, the cleaning performance is poor, so that it develops a tendency to produce defective cleaning.
Further in this type, as the angle .phi. is increased to approach .pi./2, the cleaning performance is generally improved, and there can hardly occur a toner filming phenomenon whereby toner components adhere on the surface of a toner image retaining member and a film is formed thereon. On the other hand, a bending moment is applied to the blade and the vibration of the blade is liable to occur. It thus becomes difficult to bring the blade into uniform contact with the surface of the toner image retaining member.
To stop the occurrence of the aforegoing vibration, it will do well to make the angle .phi. smaller. However, if the value of .phi. is made smaller, the cleaning performance is lowered and the toner filming phenomenon is apt to occur. Further, a foreign substance is apt to jam between the toner image retaining member and the blade, and that causes scratches on the surface of the toner image retaining member.